Optical disks draw great interest as high capacity information carrying media. Among the optical disks are magneto-optical recording disks of the magnetic field-modulation mode which are expected for their use as data files or the like. The magnetic field-modulation mode is to carry out recording by positioning an optical head and a magnetic head on opposite sides of a disk, directing laser light from the optical head to the recording layer of the disk in a DC manner to increase its temperature and at the same time, applying a modulated magnetic field across the recording layer from the magnetic head. Since this mode allows for over-write recording, there is a possibility to apply it to rewritable compact disks.
The magnetic heads used in the magnetic field-modulation mode include flying magnetic heads adapted to float on the disk surface in response to disk rotation like magnetic heads for hard disk equipment and non-flying magnetic heads spaced at a certain distance from the disk surface independent of disk rotation.
In this disclosure, non-flying magnetic heads are of concern. The non-flying magnetic heads include two types, stationary type wherein the head is spaced from the disk surface at a fixed distance and sliding type wherein the head is mounted on a slider such that the head is retracted a fixed distance from the surface of the slider in sliding contact with the disk whereby the head is maintained at the fixed distance from the disk surface during operation. In general, as the distance between the disk and the magnetic head decreases, a more intense magnetic field is applicable to the disk. The stationary magnetic head, however, can collide against the disk because the distance between the disk and the head varies due to axial run-out of the disk caused by its warpage and distortion. Then in some cases, a displacement sensor is provided in order to keep a constant disk-to-head distance. In contrast, the sliding type magnetic head can advantageously provide a constant disk-to-head distance.
The non-flying magnetic heads are suitable for use with those disks operated at relatively low rotational speeds such as compact disks (CD) since their performance does not depend on the number of disk revolutions. They are relatively free from troubles associated with irregularities and deposits on the disk surface. Additionally, they are manufactured at a low cost if the displacement sensor can be omitted.